1. Field of the Invention
The present invention relates to a medical endoscope configured to be inserted into a lumen of a subject's body to observe the subject's body.
2. Description of the Related Art
While various techniques are conventionally used to insert an endoscope into a lumen of a subject's body, a technique to insert the endoscope into an occluded lumen is very difficult. In inserting the endoscope into the occluded lumen, moreover, the inner wall of the lumen is rubbed by corners of the distal end portion of an insertion section, so that pain is inflicted on the patient.
An endoscope for urinary organs described in Jpn. Pat. Appln. KOKAI Publication No. 2000-271064 is an example of an endoscope that can be suitably inserted into such an occluded lumen. The cross section of an insertion section of this endoscope has the shape of an ellipse that agrees with the cross section of a urethra in the shape of a teardrop that is vertically long and laterally narrow. In inserting the insertion section into the urethra, therefore, the urethra is expected to be laterally extended only a little. Thus, compression of the left and right inner walls of the urethra by the insertion section can be reduced, and the ease of insertion of the insertion section is improved.
An endoscope described in Jpn. Pat. Appln. KOKAI Publication No. 10-309259 is another example of an endoscope that can be suitably inserted into an occluded lumen. This endoscope is configured to be inserted into a large intestine through the anus. The anus has the shape of an ellipse that is flattened between buttocks. In order to facilitate the insertion into the flattened occluded anus, round chamfer portions are formed by chamfering corners at the opposite edge portions of the distal end face of the insertion section according to the shape of the anus. In consequence, the ease of insertion of the insertion section into the anus is improved.
Incidentally, as shown in FIG. 21, the urethra 1 of a male person extends from the external urethral orifice 2 to the urinary bladder 4 through the urethral sphincter 3 and the prostate 6. The urethra 1 horizontally extends straight from the external urethral orifice 2 to a part just short of the urethral sphincter 3 and bends upward at this part. Further, the urethra 1 upwardly extends straight from this bent part 5 to the urinary bladder 4. Thus, the urethra 1 sharply bends at the bent part 5.
Since the urethral sphincter 3 fulfills a throttle function to close up the urethra 1, moreover, the urethra 1 is narrowed near the urethral sphincter 3. In the case of a patient whose prostate 6 is starting to hypertrophy, furthermore, the urethra 1 is narrowed near the prostate 6. Thus, the urethra 1 tends to be occluded in a region that extends from the bent part 5 to the urinary bladder 4.